• Energy Research

Thermal mass, a pivotal element in a building’s performance, functions as an indoor thermal buffer. While literature underscores its advantages, the enduring impact of thermal mass amid climate change remains uncertain. This study methodically assesses thermal mass effects in 21 Iranian cities across contemporary and future climates, juxtaposing heavyweight and lightweight constructions. The EPSAP algorithm, a generative building design method, created a dataset of two-story single-family houses. Cooling and heating demands were evaluated in EnergyPlus, accounting for current and future system design efficiencies. Future climates were simulated using EC-Earth3 model estimations for the SSP5-8.5 scenario in 2050 and 2080 timeframes. The findings reveal that the energy efficiency advantage of heavyweight over lightweight buildings will diminish by up to 0.60 kW⋅h⋅m− 2 in 2050 (40 % less than the present-day climate difference between constructions) and 0.93 kW⋅h⋅m− 2 in 2080 (63 %) for cities in central and southern regions. The performance differences between constructions will sometimes be null, making thermal mass negligible. Conversely, only three cities in Northern Iran exhibit an opposing trend for mid to very-high thermal transmittances. Regarding building geometry, heavyweight construction correlates strongly with indexes related to building compactness, while lightweight construction aligns more with glazing-related indexes. However, as climates warm or we move towards warmer regions, discernible differences between lightweight and heavyweight constructions vanish for both shape- and glazing-related indexes. In conclusion, although the use of thermal mass will be less effective, building design professionals will have greater latitude for innovative construction and design solutions. 8617-2E18-19EE | EUGÉNIO MIGUEL DE SOUSA RODRIGUES info:eu-repo/semantics/publishedVersion

Abstract Given the need to actively address the challenges of climate change, university leaders have a growing interest in reducing their campuses’ environmental impact. This article carries out a comprehensive literature review on the implemented actions and initiatives in university campuses reported in scientific publications. In addition, case studies carried out in universities are also reviewed, giving particular attention to the methods and tools used, targeting the current trends in sustainable campus scientific research. Key actions and initiatives were identified and categorized according to Energy, Buildings, Water, Waste, Transportation, Grounds, Air and Climate, and Food. Results show that the increase in energy generation on campus and the decrease of energy consumption in buildings are by far the leading policies adopted, however with limited dissemination of their impact. Moreover, there seems to be a tendency for countries with higher income economies to engage in initiatives that involve greater investment, such as the adoption of renewable energy systems or efficient buildings systems. The need to establish an integrated framework to disseminate and monitor the impact of key actions and their feasibility is suggested, in order to leverage strategic programs and actions, helping to optimize investments, and leading advances towards a sustainable university campus.

Abstract During the next decades the refurbishment of old buildings will be an essential way to contribute to the global improvement of buildings energy performance indicators. Within this context, the present paper is focused on the use of electrochromic (EC) windows, an emerging technology alternative to shading devices, to control solar gains in buildings located in Mediterranean climates. The optical properties adjustments of the EC glasses are discussed based on the incident solar radiation. The ESP-r building energy simulation software was used to study the energy savings resulting from the application of electrochromic windows, considering the comparison of several windows solutions (single, double-glazing and EC windows) and windows orientations (East, South and West). In addition, different transition ranges for the optical properties of the EC glasses are assessed through the analysis of the energy needs for space heating and cooling. The main conclusion is that EC technology is an effective option in cooling dominated buildings. The impact of EC windows is highly dependent on facade orientation, being a valid option particularly in the cases of the East and West facades. For these facades, the control set point found to be effective corresponds to an incident solar radiation on the glass of 150 W/m 2 to impose a total coloured state. For the South facade the results show no significant advantage of using EC windows.

Abstract Buildings account for 40% of total energy consumption in the European Union. The sector is expanding, which will lead to an increase of its energy consumption, if no additional measures are taken. The Directives 2002/91/EC and 2010/31/EU (recast) on the energy performance of buildings have as objective to reinforce the improvement of the energy performance of buildings, proposing the use of energy performance indicators, based on primary energy use or CO2 emissions. In this study, the limitations of the actual method are identified and a new indicator, based on exergy, is proposed, aiming to give new insights about the energy use in buildings. As a case study, a hotel building located in Coimbra (Portugal) is analysed using actual energy consumption data derived from a conducted energy audit. Besides primary energy based indicators, two more indicators were used: the primary energy ratio (PER) and exergy efficiency. Results show an estimated overall primary energy consumption of 446 kWh/(m2 year), and 49% and 17%, found as PER and exergy efficiency, respectively. From an individual analysis, the electric equipments were found as the main contributors for the primary energy consumption of the hotel; however, they present the highest exergy efficiency when compared to processes related with space air conditioning.

Abstract This paper evaluates the impact of PCM-drywalls in the annual and monthly heating and cooling energy savings of an air-conditioned lightweight steel-framed (LSF) residential single-zone building, considering real-life conditions and several European climates. A multi-dimensional optimization study is carried out by combining EnergyPlus and GenOpt tools. The CondFD-algorithm is used in EnergyPlus to simulate phase-changes. For the optimization, the PSOCC-algorithm is used considering a set of predefined discrete construction solutions. These variables are related with the thermophysical properties of the PCM (enthalpy-temperature and thermal conductivity-temperature functions), solar absortance of the inner surfaces, thickness and location of the PCM-drywalls. Several parameters are included in the model mainly those related with the air-conditioned set-points, air-infiltration rates, solar gains, internal gains from occupancy, equipment and lighting. Indices of energy savings for heating, cooling and for both heating and cooling are defined to evaluate the energy performance of the PCM-enhanced rooms. Results show that an optimum solution can be found for each climate and that PCMs can contribute for the annual heating and cooling energy savings. PCM-drywalls are particularly suitable for Mediterranean climates, with a promising energy efficiency gain of about 62% for the Csb-Coimbra climate. As for the other climates considered, values of about 10% to 46% were obtained.

AbstractBuildings thermal performance is influenced by the urban context, such as adjacent buildings shadows, block wind paths, or solar radiation reflection. For this reason, in this paper, an automated procedure is used to generate and optimize buildings’ thermal performance in a closed O-shape urban quarter with ten building blocks to determine the importance of including the surroundings in estimating the buildings’ thermal behavior. The overall shape of the urban quarter is pre-designed, being mainly residential, with several stores in the ground floor and limited to three levels. Each building will have four alternative designs created using a hybrid evolutionary strategy technique that generates building's floor plans according to practitioner's preferences and requirements. Then, a sequential variable optimization procedure coupled with dynamic simulation engine is used to explore the improvement potential of each solution by changing and adding several building elements. The final quarter design is determined by combining the best of all buildings’ solutions from thermal performance criteria.The results demonstrate the influence of urban context in the resulting building's thermal performance. Despite the building's shape is similar in the four solutions, these have significant thermal behavior difference due to their interior organization and position in the urban quarter. A comparison analysis is carried out between all building block designs. The buildings, which have exterior walls with openings facing south, have almost half degree-hours of thermal discomfort due to the combination of large openings and shading overhangs. It is also possible to conclude that generative tools, enhanced with optimization procedures, may help practitioners in designing more energy efficient buildings.

Abstract This paper evaluates the heat transfer through small thermal energy storage (TES) units filled with different phase change materials (PCMs): free-form and microencapsulated PCMs. The experimental results are very useful for benchmarking and validation of numerical models to be used in the design and optimization of new TES systems for buildings. They also allow discussing which arrangement/PCM is better for specific building applications considering the thermal regulation effect during charging, the influence of subcooling during discharging, and the influence of natural convection during both processes. During charging, the influence of the aspect ratio of the cavities on three parameters is investigated: control-temperature on the hot surface; thermal-regulation period; time required for melting the PCM in the mid-plane. During discharging, five parameters are evaluated: time for solidifying the PCM in the mid-plane; time for starting crystallization; subcooling period; phase-change temperature after subcooling; difference between the solidifying temperature and the cooled temperature due to subcooling. It was concluded that natural convection in the free-form PCM must be considered in any simulation to well describe the charging process. During discharging, subcooling must also be considered. The effects of natural convection and subcooling can be neglected when modelling cavities filled with the microencapsulated PCM.

Abstract The dynamic model of a heat storage adsorption device is presented. The adsorption module operates with the silica-gel/water pair and is capable of storing the thermal energy received from the hot water of the storage tank where it is immersed, to give it back later as adsorption heat. The module is applied to a solar thermal energy system and assessed through a set of parametric tests. It is found that higher condenser lengths and larger pre-heating water tank volumes always improve the system’s performance. For a selected fixed heat exchange area, smaller evaporator tube diameters are found to improve the system’s performance, while reducing the number of tubes of a settled diameter has a negative effect. It is also found that the system’s performance tends to decrease by increasing the main tank’s volume, thus requiring even larger adsorbers for larger tanks. Throughout this exploratory study, the adsorption system always presents higher performances when compared with a similar conventional storage system (up to 16% savings in annual backup energy), showing promising perspectives for the overall optimization and application studies, and presenting an attractive solution to increase the thermal storage capacity of solar thermal systems.